Quick connect couplings or fittings are well known and various types are described in U.S. patents. For example, U.S. Pat. Nos. 4,063,760, 3,540,760 and 3,479,068 disclose couplings of this general type, which are attached to metal tubes or flexible hoses for making fluid connections. In such a coupling, a tubular nipple part is inserted into a tubular socket part, and a resilient O-ring extends between the two parts and forms a seal. Upon insertion, the two parts become locked in assembled relation by a split lock ring or snap ring which is located in radially aligned lock grooves formed in the two parts. Prior to the assembly of the two parts, the snap ring is loosely positioned in the lock groove of the outer socket. When the nipple is inserted into the socket, the forward end of the nipple passes through and expands the snap ring, and the assembly is completed when the snap ring "snaps" into the lock groove of the nipple. The snap ring then extends into both grooves, thereby locking the parts together.
Couplings of this character have been used, for example, in making hydraulic connections in automobiles and trucks, such as the connections between the engine block and an oil cooler. An automobile or truck is constructed on a moving assembly line, and workers at stations along the line make the connections while the line is moving. It is, of course, very important, because the line moves continuously, that the socket and the nipple be securely connected together very easily and rapidly.
A problem that has been encountered in making this connection is that, at the time the nipple is pushed into the socket, the forward end of the nipple sometimes jams or catches on the snap ring which is mounted in the interior opening of the socket. As mentioned, the snap ring is split so that it can be expanded during assembly, and the ends of the ring, which are cut during manufacture, are relatively sharp and often have burrs on them. The snap ring has a substantially smaller outer diameter than the maximum diameter of the groove of the socket, and consequently the snap ring may lie in the socket groove with the exposed ends of the ring in the path of the nipple during assembly. It is possible in these circumstances for the ring or the nipple or the socket to be damaged, or for extra time to be required to assemble the parts properly.
U.S. Pat. No. 4,063,760 offers a solution to the foregoing problem, which consists of forming the snap ring with straight end portions. According to this patent, the straight end portions maintain the snap ring in the proper position to receive the end of the internal part. This solution, however, has the disadvantages that the manufacture of the snap ring is made more complicated, and that a ring with straight end portions is more difficult to install in the groove of the socket.